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The AAPG/Datapages Combined Publications Database

Pacific Section of AAPG

Abstract


Late Miocene Geology and New Oil Fields of the Southern San Joaquin Valley, 1977
Pages 56-72

Lateral Displacement of Upper Miocene Rocks . . . Along the San Andreas Fault in Central California

O. F. Huffman

Abstract

Late Miocene strata occur on both sides of the San Andreas fault for several hundred miles in central California. The unlike facies and contrasting paleogeographic situations which are found across the fault along much of this distance must have been brought together by large-scale strike-slip movement on the fault. Clastic deposits west of the San Andreas need granitic-volcanic sources east of the fault, but the only such sources are to the southeast - in one probable case, more than 110 miles away. Likewise, voluminous coarse conglomerate beds east of the fault in the southern Temblor Range require the presence of a large, highly elevated granitic and metamorphic source immediately west of the fault during the later upper Miocene. The northern Gabilan Range, about 150 miles (240 km) to the northwest, was probably the only such basement area exposed at the time; the granitic and metamorphic bedrock here is very similar to the type of gravel found within the conglomerate of the southern Temblor Range. Thus, the Temblor Range clastic rocks were deposited adjacent to the Gabilan bedrock, and the two areas subsequently have been offset by about 150 miles (240 km) of right-slip on the San Andreas fault. The Gabilan source appears to have moved northwestward along the fault during the upper Miocene; together with tentative correlations between parts of the source and parts of the clastic deposits, this suggests post-Miocene offset of 145 ± 5 miles (234 ± 8 km), post-early upper Mohnian offset of 158 ± 3 miles (254 ± 5 km), and thus 50 to 21 miles (8 to 34 km) of slip during the later upper Miocene.


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